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I am wondering on some opinions for a loop antenna.
This would be for HF, and mounted on the roof of our motorhome. Would be a 8 1/2 ft by 40 ft loop.
I am curious if anyone else has tried a similar situation, how you fed it, and how it worked, and if you had an RF problems. The motor home is primarily fiberglass, with steel and aluminum sub frame.
John
Oh cool! You live in an RV fulltime? That would be neat. That or a boat.
Sorry I can't help with the loop antenna details for you, but sounds like a cool project. Why a loop though, if I may ask? Wouldn't a 40 foot dipole with some loading and an antenna tuner work fairly well?
+1Quote:
Originally Posted by K2KLI
Or a vertical, if you bond the frame properly (or even lay out some radials on the roof) it'll perform pretty well. Only issue with that would be you couldn't use it while driving, in every video I've seen overpass beats aluminum whip every time. Sorta like scissors beats paper.
Yes, live in the MH, full-time, cool... mostly, but not when it comes to antennas.
Here's the deal. I am leaning towards a loop because I understand they are much quieter than a vertical or dipole as far as RFI, etc. When you live in a 40ft by 8 ft box, with 3 distinct electrical systems, and many other duplicate systems, things tend to be noisy, added to the fact that we have very little control over our site at any given time, an antenna that hears less noise and more signal sounds like a good idea to me!
Currently, I have a CB vertical (Solarcon A99) and a tuner (AT897) which actually work fairly well 20-6. I have it mounted on 22ft of steel mast, tied off to the rear ladder. The downfall of this system is that it is a bit ungainly to put up and take down, and as pointed out, not able to operate mobile. I am really not so concerned with the mobile part, but the easy of setup I am, and if this loop is a workable idea, where it could be permanently mounted to the MH roof, and feed with my tuner, and does as good, if not better than the Solarcon, I would be happy to ditch the solarcon. I don't like the setup, and other verticals I have discounted simply because laying out ground radials is just not an option in most parks. A traditional dipole, again, I would if I could, but not only do most parks frown upon long termers throwing wires in the trees, many don't have adequate trees, or they hang over the neighbor, erc. etc.
SO, Does anyone have any experience with rather small loops? What sort of tuning range should I expect? How should I feed it? Should I use a 4:1 balun at a midpoint and feed it with 50ohm from there?
John
http://www.isotronantennas.com/
See what you think about these compact loop antennas.
Combo models available.
Not much experience here with small loops, but during multi-band usage, I would think that you're going to have wildly varying impedence values from band to band, so the use of a balun is likely to complicate the issue, and may cause problems itself. If possible, running ladder line or twin lead (unless you're going to use an amp) all the way to a tuner would likely produce better results.Quote:
Originally Posted by N9MXX
I seem to recall a gent using a homebrew loop on his restored Volkswagen Transporter [a.k.a. Microbus]; but I'll be dipped if I can find it. I do remember the VW being white over light blue or sea-foam green.
Does this jog anyone's memory? I'll keep looking, though. :doh:
I don't have any experience with loops but I do have one concern. Assuming your motor home is at least 12 foot in height or maybe more, you might have to address the height of your loop if operating mobile. Anything over 13.5 foot might be a problem with bridges. Some cities have clearances as low as 12 foot. Maxiumum height of any vehicle operating on interstate highways is 13.5 ft without getting a permit.
Also having a string of wire running a few inches off the roof of the RV might seriously affect SWR and such.
You might look into the "DDRR" type of loops , I think there are a couple of outfits making them .
Also, some 30 years ago I built a "Folded Dipole" of sorts on a winabago for a friend following the design of the old "squalo" antenna used on 6 meters but up scaled the thing for 40 with a motorized,gear reduced tuning capacitor across the "end's" , worked quite well on 40 and even down to 6 , sorry, don't have my notes from back then but he used the thing till he died about 15 years later.
May give you something to think about.
73, John
There's an old Handbook article which discusses the DDRR; one of the tricks in getting it to work is to have a decent planar reflector several inches underneath. The author used chicken wire. One wonders how much metal is in the roof of the typical motorhome....or are they made of fiberglass, in the interest of weigh savings.Quote:
Originally Posted by W9WLS
*THAT'S* the one I was thinking about! Although I can't believe I fudged the color. http://forum.goregasm.com/images/smilies/banghead.gifQuote:
Originally Posted by WØTKX
I remember the DDRR being touted as a good CB antenna for motorhomes in the 70s. The one I saw was expensive though. Still got me thinking about it since they are low profile.Quote:
Originally Posted by N8YX
Here's a site with information on how to build one.
Interesting to note the 4" tube diameter. Looks like it would be one hellofva thing.Quote:
Originally Posted by N2NH
http://www.pa3ect.nl/
He is the man on loops here, at home or mobile 160 - 10.
Yes, it's in Dutch, but lots of pictures etc.
Follow the page magnetic loop, on the bottom is his loop on a car. (80 meter band)
Might give you some idea's if you have Q's or need translation, just ask.
That's fine. I like to look at pictures in other languages. There is a British flag you can click on however which erases all the Dutch.Quote:
Originally Posted by PA5COR
Awesome.
Thanks guys. I got lots to read now!
John